Fixation system for an elongated prosthesis

Abstract

A fixation system is disclosed for an elongated prosthesis such as a prosthetic ligament. Opposed ends of the ligament are attached to spaced apart bones such that the connections are external of the bones so as to permit a maximum of relative movement between the ligament and the bones while assuring requisite strength in tension. The design enables pretensioning of the ligament, guards against abrasion of the ligament by reason of moving contact with the bones, and is adjustable to accommodate a variety of required sizes.

I claim: 
     
       1. A prosthetic ligament assembly for connecting first and second spaced apart bones comprising: first retention means fixed to the first bone having a first bore therethrough extending between a minor opening of reduced cross sectional area facing toward the second bone and a major opening of increased cross sectional area facing away from the second bone, the bore defining a first seating surface therein;   said first retention means including a first attachment member having a minor end of reduced cross sectional area and a major end of increased cross sectional area shaped similarly to said first seating surface for mating engagement therewith, said major end of said first attachment member being greater in magnitude than the minor opening in said first retention means;   second retention means fixed to the second bone having a second bore therethrough extending between a minor opening of reduced cross sectional area facing toward the first bone and a major opening of increased cross sectional area facing away from the first bone, the second bore defining a frusto-conical second seating surface;   an elongated prosthetic ligament extending between first and second ends and being attached at said first end to said first attachment member; and   said second retention means including adjustable mounting means for selectively attaching said second end of said prosthetic ligament to said second retention means to achieve a predetermined tension therein.   
     
     
       2. A prosthetic ligament assembly as set forth in claim 1 wherein said adjustable mounting means includes:   an elongated cylindrical externally threaded anchor member attached at one end to said second end of said prosthetic ligament and extending through the second bore in said second retention means; and   a second attachment member frusto-conical shaped similarly to the bore in said second retention means and having a threaded bore extending therethrough for threaded engagement with said anchor member;   enabling said second frusto-conical attachment member to be screwed into mating engagement with said second seating surface until the predetermined magnitude of tension in said prosthetic ligament is achieved.   
     
     
       3. A prosthetic ligament assembly as set forth in claim 1 wherein said first seating surface is a frusto-conical surface; and   wherein said first attachment member is frusto-conical shaped.   
     
     
       4. A prosthetic ligament assembly as set forth in claim 1 wherein said first retention means is generally cylindrical, being externally threaded for fixation to the first bone and having a longitudinal axis, the first bore being aligned with said longitudinal axis; and   wherein said second retention means is generally cylindrical, being externally threaded for fixation to the second bone and having a longitudinal axis, the second bore being aligned with said longitudinal axis.   
     
     
       5. A prosthetic ligament assembly as set forth in claim 2 wherein said first and second ends of said prosthetic ligament include loop members integral therewith;   wherein said anchor member includes a loop member at said one end linked with said loop member at said second end of said prosthetic ligament; and   wherein said first attachment member includes a loop member at said minor end linked with said loop member at said first end of said prosthetic ligament.   
     
     
       6. A prosthetic ligament assembly as set forth in claim 2 including: first coupling means external of the first bone for connecting said first attachment member to said prosthetic ligament to resist tensile loading therebetween while otherwise permitting relative movement between said first attachment member and said prosthetic ligament; and   second coupling means external of the second bone for connecting said anchor member to said prosthetic ligament to resist tensile loading therebetween while otherwise permitting relative movement between said anchor member and said prosthetic ligament.   
     
     
       7. A prosthetic ligament assembly as set forth in claim 6 wherein said first coupling means includes a first pair of mutually linked loop members integral, respectively, with said first attachment member and with said prosthetic ligament; and   wherein said second coupling means includes a second pair of mutually linked loop members integral, respectively, with said anchor member and with said prosthetic ligament.   
     
     
       8. A prosthetic ligament assembly for connecting first and second spaced apart bones comprising: an elongated prosthetic ligament extending between first and second ends;   first retention means fixed to the first bone having a first bore extending therethrough between a minor opening of reduced cross sectional area facing toward the second bone and a major opening of increased cross sectional area facing away from the second bone, the bore defining a first seating surface therein, said first retention means including a first attachment member having a minor end of reduced cross sectional area and a major end of increased cross sectional area shaped similarly to said first seating surface for mating engagement therewith, said major end of said first attachment member being greater in magnitude than the minor opening in said first retention means;   second retention means fixed to the second bone having a second bore extending therethrough between a minor opening of reduced cross sectional area facing toward the first bone and a major opening of increased cross sectional area facing away from the first bone, the second bore defining a frusto-conical second seating surface therein, said second retention means including adjustable mounting means for selectively attaching said second end of said prosthetic ligament to said second retention means to achieve a predetermined tension therein;   first coupling means external of the first bone for connecting said first end of said prosthetic ligament to said first retention means to resist tensile loading therebetween while otherwise permitting relative movement therebetween; and   second coupling means external of the second bone for connecting said second end of said prosthetic ligament to said second retention means to resist tensile loading therebetween while otherwise permitting relative movement therebetween.   
     
     
       9. A prosthetic ligament assembly as set forth in claim 8 wherein said adjustable mounting means includes:   an elongated cylindrical externally threaded anchor member attached at one end to said second end of said prosthetic ligament and extending through the second bore in said second retention means; and   a second attachment member frusto-conical shaped similarly to the bore in said second retention means and having a threaded bore extending therethrough for threaded engagement with said anchor member; enabling said second frusto-conical attachment member to be screwed into mating engagement with said second seating surface until the predetermined magnitude of tension in said prosthetic ligament is achieved.   
     
     
       10. A prosthetic ligament assembly as set forth in claim 8 wherein said first seating surface is a frusto-conical surface; and   wherein said first attachment member is frusto-conical shaped.   
     
     
       11. A prosthetic ligament assembly as set forth in claim 8 wherein said first retention means is generally cylindrical, being externally threaded for fixation to the first bone and having a longitudinal axis, the first bore being aligned with said longitudinal axis; and   wherein said second retention means is generally cylindrical, being externally threaded for fixation to the second bone and having a longitudinal axis, the second bore being aligned with said longitudinal axis.   
     
     
       12. A prosthetic ligament assembly as set forth in claim 9 wherein each of said first and second ends of said prosthetic ligament includes a loop integral therewith;   wherein said anchor member includes a loop member at said one end linked with said loop member at said second end of said prosthetic ligament; and   wherein said first attachment member includes a loop member at said minor end linked with said loop member at said first end of said prosthetic ligament.   
     
     
       13. A prosthetic ligament assembly as set forth in claim 8 wherein said first coupling means includes a first pair of mutually linked loop members integral, respectively, with said first attachment member and with said prosthetic ligament; and   wherein said second coupling means includes a second pair of mutually linked loop members integral, respectively, with said anchor member and with said prosthetic ligament.   
     
     
       14. A prosthetic ligament assembly for connecting first and second spaced apart bones comprising: an elongated prosthetic ligament extending between first and second ends;   first retention means having a threaded bore therethrough fixed to the first bone and including a first attachment member threadedly engaged with the threaded bore, said first attachment member including an integral loop member generally facing the second bone; and   second retention means having a smooth bore therethrough fixed to the second bone and including an externally threaded second attachment member slidably received in the smooth bore, said second attachment member including an integral loop member generally facing the first bone and a nut fastener threadedly engaged with said second attachment member;   said prosthetic ligament including integral loop members at said first and second ends, respectively, mutually linking said loop members on said first and second attachment members enabling said nut fastener to be screwed into mating engagement with said second retention means until a predetermined magnitude of tension in said prosthetic ligament is achieved.